1. Field of the Invention
The present invention relates to a circuit board laminated module in which a second circuit board is mounted on a first circuit board, and a semiconductor chip is bare-chip mounted on the upper surface of the second circuit board. Besides, the present invention relates to an electronic equipment in which a first circuit board as a mother board has a structure of the circuit board laminated module.
2. Description of the Related Art
An electronic product is miniaturized, is reduced in thickness, is improved in functionality and is improved for higher frequency. A circuit section of the electronic product is generally constructed by mounting semiconductor integrated circuits (hereinafter referred to as IC chips) and other many circuit parts on a printed wiring board.
In the IC chip constituting the electronic product, an improvement in fineness and improvement in integration advance, and a system LSI is developed which realizes the whole function block, which is conventionally constructed of a printed wiring board, plural ICs and other circuit parts, by one semiconductor chip.
On the other hand, a printed wiring board and a mounted part are required to support higher frequency and higher speed, and to achieve an improvement in fineness and higher integration.
For the miniaturization and reduction in thickness of an electronic equipment, it is requested that in addition to an IC chip, plural circuit elements (devices), such as passive elements of inductors, capacitors and resistors, are mounted in a small space on the same board. In order to meet the request, a system in package (SiP) in which plural IC chips and passive parts are mounted on one package is put into practical use.
Besides, for further miniaturization and reduction in height (reduction in thickness), the technology of forming passive elements in the inside of a printed wiring board is actively developed. By this technology, the cost of an external part which is difficult to incorporate in an IC under present circumstances is reduced, and further, it becomes possible to prevent the external part from impeding the miniaturization and reduction in height of the whole board.
When the miniaturization and reduction in height advance, there is a fear that a phenomenon occurs in which at the time of circuit operation mainly including an active element, the characteristic of a surrounding passive element is changed by radiated electromagnetic wave or electromagnetic field emitted from the circuit, this is fed back to the circuit and the circuit characteristic is deteriorated.
In order to prevent the electromagnetic interference as stated above, it is necessary to prevent the influence by suitably forming a shield structure.
However, for example, in a passive element, such as an inductor, which itself generates an electromagnetic field, when a conductive layer kept at ground potential exists in the vicinity thereof, an eddy current loss is generated by magnetic flux entering the layer of the ground potential. Then, since the density of the magnetic flux returning to the inductor is reduced, and the Q value and the inductance (L value) are reduced.
As a countermeasure to avoid such disadvantage, a shield layer is separated from an inductance (see, for example, JP-A-10-199734 (patent document 1)).